diff --git a/modules/fdlibm/src/math_private.h b/modules/fdlibm/src/math_private.h
--- a/modules/fdlibm/src/math_private.h
+++ b/modules/fdlibm/src/math_private.h
@@ -12,16 +12,17 @@
 /*
  * from: @(#)fdlibm.h 5.1 93/09/24
  * $FreeBSD$
  */
 
 #ifndef _MATH_PRIVATE_H_
 #define	_MATH_PRIVATE_H_
 
+#include <cfloat>
 #include <stdint.h>
 #include <sys/types.h>
 
 #include "fdlibm.h"
 
 #include "mozilla/EndianUtils.h"
 
 /*
